Method and apparatus for secondary synchronization in internet of things

1. A method for acquiring, by a receiving apparatus, synchronization in the Internet of things based on a secondary synchronization signal received from a transmitting apparatus, the method comprising: extracting a frequency domain sample by applying channel estimation to a time domain sample of the secondary synchronization signal; and estimating a physical cell ID (PCI) and frame timing (FT) based on decorrelation between a frequency domain standard signal of the secondary synchronization signal and the frequency domain sample, wherein the extracting includes: removing a cyclic prefix (CP) from the time domain sample; down-sampling a sample from which the CP is removed; and performing fast Fourier transform (FFT) on the down-sampled sample, wherein the estimating includes: calculating a first value by performing decorrelation between Fourier series (FS) sequences included in the frequency domain standard signal and the frequency domain sample; calculating a second value by performing decorrelation between a Zadoff Chu (ZC) sequence included in the frequency domain standard signal and the first value; calculating a third value by performing decorrelation between a scrambling sequence included in the frequency domain standard signal and the second value; and estimating the PCI and the FT using the first value, the second value, and the third value.

2. The method of claim 1 , wherein the estimating further includes calculating a fourth value by performing a cyclic shift (CS) combining on the third value.

3. The method of claim 2 , wherein the estimating of the PCI and the FT includes estimating the PCI and the FT using the first to fourth values.

4. The method of claim 2 , wherein after the calculating of the first value, the calculating of the second value, the calculating of the third value, and the calculating of the fourth value are repeatedly performed by the accumulated number of times, the estimating of the PCI and the FT is performed.

5. The method of claim 1 , wherein: the first value is calculated only by sign conversion instead of a multiplication operation, and the third value is calculated only by the sign conversion instead of the multiplication operation.

6. The method of claim 1 , wherein the FT is 80 ms FT.

7. A method for acquiring, by a terminal, synchronization in the Internet of things based on a secondary synchronization signal received from a base station, the method comprising: extracting a frequency domain sample from a time domain sample of the secondary synchronization signal, wherein the extracting includes: removing a cyclic prefix (CP) from the time domain sample; down-sampling a sample from which the CP is removed; and performing fast Fourier transform (FFT) on the down-sampled sample; and estimating a physical cell ID (PCI) and 80 ms frame timing (FT) based on decorrelation between a sequence included in a frequency domain standard signal of the secondary synchronization signal and the frequency domain sample, wherein the estimating includes: calculating a first value by performing decorrelation between Fourier series (FS) sequences included in the frequency domain standard signal and the frequency domain sample; calculating a second value by performing decorrelation between a Zadoff Chu (ZC) sequence included in the frequency domain standard signal and the first value; calculating a third value by performing decorrelation between a scrambling sequence included in the frequency domain standard signal and the second value; calculating a fourth value by performing cyclic shift (CS) combining on the third value; and estimating the PCI and the FT by using the first to fourth values.

8. The method of claim 7 , wherein after the calculating of the first value, the calculating of the second value, the calculating of the third value, and the calculating of the fourth value are repeatedly performed by the accumulated number of times, the estimating of the PCI and the FT is performed.

9. The method of claim 7 , wherein: the first value is calculated only by an addition calculation instead of a multiplication operation, and the third value is calculated only by an addition calculation instead of the multiplication operation.

10. A receiving apparatus comprising: an analog-digital converter sampling a secondary synchronization signal received from a transmitting apparatus into a digital signal to generate a first sampling signal: a filter unit filtering the first sampling signal; and a synchronization detector extracting a frequency domain sample by performing channel estimation on the filtered first sampling signal and estimating a physical cell ID (PCI) and 80 ms frame timing (FT) based on decorrelation between a frequency domain standard signal of the secondary synchronization signal and the frequency domain sample, wherein the synchronization detector: removes a cyclic prefix (CP) from the first sampling signal; down-samples a sample from which the CP is removed; and performs fast Fourier transform (FFT) on the down-sampled sample to extract the frequency domain sample, wherein the synchronization detector: calculates a first value by performing decorrelation between Fourier series (FS) sequences included in the frequency domain standard signal and the frequency domain sample, calculates a second value by performing decorrelation between a Zadoff Chu (ZC) sequence included in the frequency domain standard signal and the first value, calculates a third value by performing decorrelation between a scrambling sequence included in the frequency domain standard signal and the second value, and a fourth value by performing cyclic shift (CS) combining on the third value, and estimates the PCI and the FT by using the first to fourth values.

11. The receiving apparatus of claim 10 , wherein the synchronization detector repeatedly calculates the first to fourth values by a predetermined accumulated number of times and then estimates the PCI and the FT.

12. The receiving apparatus of claim 10 , wherein the first value is calculated only by an addition calculation instead of a multiplication operation and the third value is calculated only by an addition calculation instead of the multiplication operation.